Machines for backfilling trenches are well known in the art. Some machines may use augers, typical examples being shown in U.S. Pat. Nos. 3,934,363, 4,283,867, 5,353,529, 5,479,728, and 6,434,861. Some of these devices may be provided with additional structure for tamping or compacting the backfill material after it has been placed in the trench.
In addition to the auger class of machines, another type of machine uses a pair of blades to push the backfill material back into the trench. Typical machines are shown in U.S. Pat. Nos. 3,195,249, 3,471,953, 3,797,582, 4,802,293, and 7,104,726. Other machinery is shown in U.S. Pat. Nos. 3,181,258, 4,507,012, 4,539,765, and 4,842,441.
Most of the patented designs referred to above are not designed for use with paved roads. Thus paved roads usually require a backfill to a prescribed height, and then typically a first fill of base, a second fill of a binder, and a top fill of asphalt, which fills may be of varying heights and widths, the fills in the trade typically being called lifts.
When laying pipe, such as a waterline, in a street paved with asphalt it is conventional to cut the pavement to the desired width necessary for excavation of pipeline trench. The cut pavement is then removed to provide a clean uniform edge with minimum disturbance of the remaining pavement. After the pipe is layed, material removed from the trench may be used for backfill if suitable and if permitted by local codes, otherwise crushed rock and cement or the like is used for backfill. The trench is backfilled so that the top surface of the compacted upper lift of backfill after compacting matches the bottom of the adjacent pavement. Asphalt is then placed on the backfill. Typically three lifts of asphalt are placed over the compacted backfill, the first lift being a base of course aggregate, the next lift being a binder course, and the final lift being a top course. Each of the various lifts is typically dumped onto the backfill or the previous lift of asphalt, and is then hand shoveled to that it fully covers the previous lift with a slight crown so that after rolling it is of the desired height. For example, the first lift of course aggregate asphalt is placed in such a manner that after rolling its top surface will be 3 inches below the surface of the adjacent pavement. The next lift, the binder lift of asphalt, will be hand worked so that after rolling it will be about 1½ inches below the surface of the pavement. The top wearing course is then placed so that its initial height is about 1 inch above the top surface of the adjacent pavement so that, after rolling, its height is at the same height as the adjacent pavement.